In the fabrication of semiconductor devices, it is often necessary to perform process steps on what is commonly known as the backside of the devices. This is most commonly done while the devices are in wafer form. Typical backside process steps include thinning, the implantation of impurities, the activation of implanted impurities and the deposition of backside metal contacts.
One well known and widely employed method of backside processing includes mounting a substantially processed wafer face down on a vacuum chuck. By substantially processed, it is meant that frontside processing is virtually complete and only backside processing steps remain. The face of the wafer is generally protected or some type of pad is disposed on the vacuum chuck itself. Once the wafer is held in place on the vacuum chuck, the backside of the wafer is ground back or thinned to a desired thickness. The wafer is typically thinned by a chemical/mechanical polishing method. It is well known to finish the thinning only chemically so that backside surface damage is minimized.
Following the thinning of the wafer, it is removed from the vacuum chuck and backside metal is deposited by methods well known in the art. Following the deposition of backside metal, the wafer is mounted face up on a plastic adhesive and is sawed into individual dice. Wafer saws may be adjusted so that they will completely cut through the wafer without substantially cutting the plastic adhesive on which the wafer is mounted. The plastic adhesive holds the diced wafer in place so that the individual dice may be picked and placed from the plastic.
Although the process set forth above works very well for some applications, it requires a significant amount of wafer handling. Especially when dealing with very thin wafers, there is tendency for the wafers to break during handling. Breakage is often prior to mounting on the plastic adhesive.
Accordingly, it would be desirable to have a method useful in the backside processing of semiconductor wafers that allows very thin wafers to be backside processed and prepared for packaging that results in significantly reduced wafer breakage.